Filter panel support grids are well known. Existing grids use formed steel sheets as segments that are welded together to form a unitary grid structure. This requires large assemblies to be constructed and finished on the site at which they are to be installed. Consequently, manufacturing costs are high and the lack of control over the manufacturing environment may result in quality problems. Also, welded structures lack an aesthetic appearance which is desired in many applications.
As an alternative to welded structures, some existing ceiling grids employ extruded aluminum segments which are mechanically attached to provide a unitary structure. These attachment methods are generally cumbersome, requiring further modification of the grid segments by precise machining. Such methods employ attachment methods which result in a grid structure lacking in rigidity.
In an industrial manufacturing environment in which ceiling filters are typically employed, there is a need for overhead lighting and for suspension of equipment and materials. Known ceiling grid structures suspend lights from the ceiling and hang lightweight objects from screws which engage the lower surfaces of grid rails. Such threaded connections have limited capacity to carry heavy weights. Therefore, numerous screw holes are required for carrying heavy loads. In addition, when equipment and lights are removed, screws are removed from the grid; the resulting empty screw holes present an unattractive appearance.
The use of overhead lighting in conjunction with existing filter panel support grids has several disadvantages because the necessary light fixtures extend below the ceiling lower surfaces. First, such light fixtures prevent any dividers or walls from reaching the ceiling surface when suspended below a light fixture. This impairs the air flow isolation that may be desired between zones. Second, clean room ceiling height is generally limited and at a premium due to the equipment and duct work-required above the ceiling and below the floor. The suspension of light fixtures below the ceiling serves further to reduce this already limited ceiling height. Third, the suspension of lights below the ceiling surface creates a safety and contamination risk, as the fixtures are susceptible to accidental impact which may cause damage or dislodge contaminants.
The use of suspended light fixtures limits the capacity and flexibility to hang further items from the ceiling structure. A suspended item is fixed once installed, and the installation labor must be repeated if the fixture is to be moved, even if only by a small amount. The installation of hanging walls and dividers is limited to orthogonal orientations directly aligned with grid structure elements. A suspended light fixture may not be installed in the same location as a suspended wall, nor may a wall intersect a suspended light structure without being spaced below the light, leaving a substantial gap between the wall and ceiling. In addition, structures suspended below lights impair access to the light, making the removal of light tubes difficult or impossible.
Light fixtures that are suitable for use on existing filter panel support grids are generally too bulky for a low profile, retro-fit installation. In addition, these fixtures are generally designed as needlessly rigid units which are costlier than required and more cumbersome to install.
From the foregoing it will be recognized that there is a need for a filter support structure that overcomes these drawbacks of the prior art by providing illumination without creating safety and contamination problems, and without restricting the flexibility of wall arrangements. The present invention satisfies this need. The foregoing and additional features and advantages of the present invention will be more readily apparent from the following detailed description which proceeds with reference to the accompanying drawings.